Electronic control device including interrupt wire

ABSTRACT

An electronic control device includes a substrate, a plurality of component-mounted wires disposed on the substrate, a plurality of electronic components mounted on the respective component-mounted wires, a common wire disposed on the substrate and coupled with each of the electronic components, an interrupt wire coupled between one of the component-mounted wires and the common wire, a connection wire via which the interrupt wire is coupled with one of the common wire and the one of the component-mounted wires, and a solder disposed between each of the electronic components and a corresponding one of the component-mounted wires and having a lower melting point than the interrupt wire. The interrupt wire is configured to melt in accordance with heat generated by an overcurrent so as to interrupt a coupling between the one of the component-mounted wires and the common wire.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is based on and claims priority to JapanesePatent Application No 2011-22924 filed on Feb. 4, 2011 the disclosure ofwhich is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an electronic control device includingan interrupt wire for overcurrent protection.

BACKGROUND

Conventionally, an electronic control device includes a fuse in case ofa fault in the electronic control device. In an electronic controldevice in which small components are densely arranged, because ashort-circuit current generated at a short-circuit fault in the smallcomponents does not reach a high current, it takes a long time tointerrupt by the fuse. Especially when a large fuse is used forprotecting a plurality of electronic control devices so as to reduce thenumber of fuses and a cost, it takes a longer time. Thus, temperaturesof the components may be increased at an interruption and a voltage dropin a power supply wire and the like may be caused for a long time. Incontrast, in a common wire, such as a power supply wire (e.g., a batterypath and a ground path), that supplies electric power required foroperating many circuits and many components mounted in accordance withadvancement and diversification of electronic control, a relatively highcurrent flows. Thus, an interrupting current of a large fuse disposed ina common wire path is further increased, and the electronic controldevice does not secure a sufficient interrupt performance at ashort-circuit fault in each circuit or each component. Theabove-described issue becomes noticeable, for example, in an electroniccontrol device for a vehicle used at a higher temperature and includingmany mounted devices.

JP-A-2007-311467 discloses a printed circuit board control device inwhich an interrupt wire is disposed in a power supply wire in eachsubstrate. If an overcurrent flows, the interrupt wire melts and thepower sully wire is interrupted in each substrate or each device.

On a substrate in which components are densely mounted, acomponent-mounted wire, such as a land, on which an electronic componentis mounted, and a common wire shared by a plurality of electroniccomponents including the electronic component are disposed adjacent toeach other. Thus, when an interrupt wire is disposed in a wire couplingthe component-mounted wire and the common wire, neat generated by anovercurrent at the interrupt wire is transmitted to thecomponent-mounted wire and the common wire. Thus, a temperature rise ofthe interrupt wire may vary and an interrupt performance of theinterrupt wire may be decreased. As examples of the decrease in theinterrupt performance, a melting time and an interrupting current of theinterrupt wire may vary or may increase.

SUMMARY

In view of the foregoing problems, it is an object of the presentinvention to provide an electronic control device, which can restrict adecrease in an interrupt performance by an interrupt wire.

An electronic control device according to an aspect of the presentinvention includes a substrate, a plurality of component-mounted wires,a plurality of electronic components, a common wire, an interrupt wire,a connection wire and a solder. The component-mounted wires are disposedon the substrate. The electronic components are mounted on therespective component-mounted wires. The common wire is disposed on thesubstrate and is coupled with each of the electronic components. Theinterrupt wire is coupled between one of the component-mounted wires andthe common wire. The interrupt wire is configured to melt in accordancewith heat generated by an overcurrent so as to interrupt a couplingbetween the one of the component-mounted wires and the common wire viathe interrupt wire. The interrupt wire is coupled with a connectionobject, which is one of the common wire and the one of thecomponent-mounted wires, via the connection wire. The solder is disposedbetween each of the electronic components and a corresponding one of thecomponent-mounted wires. The solder has a lower melting point than theinterrupt wire. The connection wire has a first end portion adjacent tothe interrupt wire and a second end portion adjacent to the connectionobject. A cross-sectional area of the first end portion of the interruptwire is smaller than a cross-sectional area of the second end portion ofthe interrupt wire.

In the above electronic control device, when heat generated at theinterrupt wire is transmitted to the connection object via theconnection wire, the heat is gradually diffused in the connection wireand is not absorbed excessively to the connection object. Therefore,even when the connection object is mounted on one of thecomponent-mounted wire with the solder having a lower melting point thanthe interrupt wire, the solder is less likely to be melted by the heatfrom the interrupt wire. Accordingly, a temperature rise in theinterrupt wire can be restricted and a decrease in an interruptperformance of the interrupt wire can be restricted.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and advantages of the present invention will be morereadily apparent from the following detailed description when takentogether with the accompanying drawings. In the drawings:

FIG. 1 is a block diagram showing a vehicle control system including atraction control device according to a first embodiment of the presentdisclosure;

FIG. 2 is a diagram showing a part of the traction control deviceaccording to the first embodiment;

FIG. 3 is a cross-sectional view of the traction control device takenalong line III-III in FIG. 2;

FIG. 4 is an enlarged view of a portion around an interrupt wire of thetraction control device shown in FIG. 2;

FIG. 5A and FIG. 5B are diagrams showing two examples of a part of atraction control device according to a first modification of the firstembodiment;

FIG. 6 is a diagram showing a part of a traction control deviceaccording to a second modification of the first embodiment;

FIG. 7 is a diagram showing a part of a traction control deviceaccording to a third modification of the first embodiment;

FIG. 8 is a diagram showing a part of a traction control deviceaccording to a second embodiment of the present disclosure;

FIG. 9 is an enlarged view of a portion around an interrupt wire of thetraction control device shown in FIG. 8;

FIG. 10A and FIG. 10B are diagrams showing two examples of a part of atraction control device according to a modification of the secondembodiment;

FIG. 11 is a diagram showing a part of a traction control deviceaccording to a third embodiment of the present disclosure;

FIG. 12 is a diagram showing a part of a traction control deviceaccording to a fourth embodiment of the present disclosure;

FIG. 13 is an enlarged view of a portion around an interrupt wire of thetraction control device shown in FIG. 12;

FIG. 14 is a diagram showing a device including a test interrupt wireand a test opening portion;

FIG. 15 is a graph showing a relationship between an interruptingcurrent and a melting time of the test interrupt wire in each case wherethe test opening portion is defined and where the test opening portionis not defined;

FIG. 16 is a diagram showing a part of a traction control deviceaccording to a modification of the fourth embodiment; and

FIG. 17 is a diagram showing a configuration of a traction controldevice according to a fifth embodiment of the present disclosure.

DETAILED DESCRIPTION First Embodiment

An electronic control device according to a first embodiment of theresent disclosure will be described with reference to drawings. Theelectronic control device according to the present embodiment can besuitably used as a traction control device 20 included in a vehiclecontrol system 11. As shown in FIG. 1, the vehicle control system 11includes a plurality of electronic control devices 12 that include thetraction control device 20, an engine electronic control unit (ECU), abrake ECU, a steering ECU, a body ECU, a navigation device, and thelike.

The traction control device 20 restricts an acceleration slip of adriving wheel. In a vehicle control such as a running control, thetraction control device 20 is less important than other electroniccontrol devices.

The electronic control devices 12 including the traction control device20 are electrically coupled with a battery 13 via one of fuses 14 a, 14b used for overcurrent protection. The battery 13 is a direct-currentpower source. Because each of the fuses 14 a, 14 b is disposed on apower supply path for supplying electric power to many electroniccontrol devices, each of the fuses 14 a, 14 b may be a large fuse for 15A or. 20 A. When one of the electronic control devices 12 coupled withthe fuse 14 a has abnormality and an overcurrent greater than apredetermined current value is generated, the fuse 14 a blows out by theovercurrent, and a power supply via the fuse 14 a is interrupted. Thus,an adverse influence to the other electronic control devices 12 can berestricted. In an example shown in FIG. 1, each of the electroniccontrol devices 12 is electrically coupled with the battery 13 via oneof the fuses 14 a, 14 b. However, all the electronic control devices 12may also be electrically coupled with the battery 13 via a single fuse,or each of the electronic control devices 12 may also be electricallycoupled with the battery 13 via one of more than two fuses.

The traction control device 20 according to the present embodiment willbe described with reference to FIG. 2 to FIG. 4.

The traction control device 20 includes the circuit substrate 21 housedin a casing (not shown). On the circuit substrate 21, a plurality ofelectronic components 22 for restricting an acceleration slip isdensely-mounted on the circuit substrate 21. The circuit substrate 21 iselectrically coupled with an external device and other electroniccontrol devices 12 via, for example, a connector, and restricts anacceleration slip of the driving wheel based on a predetermined signal.

Each of the electronic components 22 on the circuit substrate 21 iselectrically coupled with a power supply wire 23. The power supply wire23 is coupled with the battery 13 by the power supply path via the fuse14 a and supplies electric power from the battery 13 to each of theelectronic components 22. Thus, the power supply wire 23 is an exampleof a common wire shared by the electronic components 22.

As shown in FIG. 2 and FIG. 3, one of the electronic components 22 onthe circuit substrate 21 is a ceramic capacitor 24. The ceramiccapacitor 24 may be formed by stacking a high-pemittivity ceramic madeof barium titanate and an internal electrode in layers for improvingtemperature characteristics and frequency characteristics, and therebyhaving a large capacity with a small size.

The ceramic capacitor 24 has outside electrodes 24 a on either endsthereof. The outside electrodes 24 a are mounted on respective lands 26via solders 25. Between one of the lands 26 and the power supply wire23, an interrupt wire 30 is coupled. The interrupt wire 30 melts by heatgenerated by an overcurrent and interrupts the electric coupling betweenthe land 26 and the power supply wire 23 via the interrupt wire 30.Thus, the interrupt wire 30 can achieve an overcurrent protectiondepending on the circuit substrate 21.

The interrupt wire 30 has a wire width sufficiently smaller than a wirewidth of the power supply wire 23. The wire width means a dimension in adirection that is perpendicular to a direction of electric current on asurface of the circuit substrate 21. For example, the interrupt wire 30has a wire width within a range from 0.2 mm to 0.3 mm, and the powersupply wire 23 has a wire width of 2 mm. The lands 26 can work ascomponent-mounted wires.

One end of the interrupt wire 30 is coupled with the power supply wire23 via a connection wire 40, and the other end of the interrupt wire 30is coupled with the land 26 via a connection wire 50. The connectionwires 40 and 50 are made of conductive material, such as copper, in amanner similar to the interrupt wire 30 and the power supply wire 23.The connection wires 40 and 50 have a greater conductor volume than theinterrupt wire 30. The connection wire 40 coupled with the power supplywire 23 can work as a first connection wire, and the connection wire 50coupled with the land 26 can work as a second connection wire.

As shown in FIG. 4, a wire width of the connection wire 40 increasestoward the power supply wire 23 in a stepwise manner so that across-sectional area S1 a at an end of the connection wire 40 adjacentto the interrupt wire 30 is smaller than a cross-sectional area S1 b atthe other end of the connection wire 40 adjacent to the power supplywire 23. Similarly, a wire width of the connection wire 50 increasestoward the land 26 in a stepwise manner so that a cross-sectional areaS2 a at an end of the connection wire 50 adjacent to the interrupt wire30 is smaller than a cross-sectional area S2 b at the other end of theconnection wire 50 adjacent to the land 26.

As shown in FIG. 3, the interrupt wire 30 has a wire thickness thinnerthan wire thicknesses of the connection wires 40 and 50. In FIG. 3,thicknesses of wires, such as an interrupt wire 30, are shown in amagnified way. The wire thickness means a dimension in a direction thatis perpendicular to the circuit substrate 21. On an inside of theinterrupt wire 30, a heat transmission restriction member 27 isdisposed. The heat transmission restriction member 27 is made of, forexample, resist material, so that the heat restriction member 27restricts transmission of heat toward an inside of the circuit substrate21. The interrupt wire 30 is easily shaped to have the thinner thicknessthan the connection wires 40 and 50 by disposing the heat transmissionrestriction member 27 on the inside of the interrupt wire 30 duringshape formation of the interrupt wire 30. Further, the cross-sectionalareas S1 a and S2 a become smaller by disposing the heat transmissionrestriction member 27.

In the traction control device 20 having the above-describedconfiguration, for example, when a short-circuit fault occurs in theceramic capacitor 24 and an overcurrent flows in the interrupt wire 30,the interrupt wire 30 generates heat in accordance with the overcurrent.When the generated heat becomes greater than a predeterminedtemperature, the interrupt wire 30 melts, and the electric coupling viathe interrupt wire 30 is interrupted. Accordingly, the other electroniccomponents 22 coupled with the power supply wire 23 can be protectedagainst the overcurrent. The current at interruption is not high enoughto blow the fuse 14 a. Thus, the damage of the traction control device20 does not influence to the other electronic control devices 12supplied with power via the fuse 14 a. A time from generation of theovercurrent to the melting of the interrupt wire 30 is a fewmilliseconds, and a melting time of each of the fuses 14 a, 14 b isgenerally about 0.02 seconds. Thus, the overcurrent protection can beappropriately achieved even to an electronic control device or anelectronic component that is required to improve a processing speed.

In particular, heat generated at the interrupt wire 30 by an overcurrentis transmitted to the power supply wire 23 via the connection wire 40.When the interrupt wire 30 having a small wire width is directly coupledwith the power supply wire 23 having a large wire width, the heat iseasily transmitted to the power supply wire 23. Thus, the temperature ofthe interrupt wire 30 decreases and the temperature decrease has avariation. Similarly, when the interrupt wire 30 is directly coupledwith the land 26, the temperature of the interrupt wire 30 decreases andthe temperature decrease has a variation. Further, since the heattransmitted from the interrupt wire 30 is concentrated at a connectingportion between the interrupt wire 30 and the land 26, the solder 25adjacent to the interrupt wire 30 melts and a melt conductor generatedby the melting of the interrupt wire 30 may scatter around theconnecting portion between the interrupt wire 30 and the land 26.

In the traction control device 20 according the present embodiment, theheat generated at the interrupt wire 30 is transmitted to the powersupply wire 23 via the connection wire 40, which has the smallercross-sectional area S1 a adjacent to the interrupt wire 30 comparedwith the cross-sectional area S1 b adjacent to the power supply wire 23.Additionally, the heat generated at the interrupt wire 30 is transmittedto the land 26 via the connection wire 50, which has the smallercross-sectional area S2 a adjacent to the interrupt wire 30 comparedwith the cross-sectional area S2 b adjacent to the land 26.

Thus, when heat generated at the interrupt wire 30 by an overcurrent istransmitted to the power supply wire 23 via the connection wire 40 andis transmitted to the land 26 via the connection wire 50, because heatrequired for melting the interrupt wire 30 is held by the connectionwires 40 and 50, the heat is not absorbed excessively to the powersupply wire 23 and the land 26 compared with a case where heat istransmitted directly to the power supply wire 23 and the land 26.Accordingly, a variation in a temperature rise of the interrupt wire 30can be restricted, and a variation in the melting time can be restrictedeven when the melting time is short as described above. Thus, a decreasein an interrupt performance of the interrupt wire 30 can be restricted.In particular, the heat generated at the interrupt wire 30 by theovercurrent is gradually diffused in the connection wire 50 and iswidely transmitted to the land 26. Thus, a local temperature rise in theland 26 can be restricted. Therefore, even when the ceramic capacitor 24is mounted on the land 26 with the solder 25 having a lower meltingpoint than a melting point of the interrupt wire 30, the solder 25 isless likely to be melted by the heat from the interrupt wire 30. Incontrast, during a steady state of the traction control device 20, theinterrupt wire 30 generates heat due to the current flowing through theinterrupt wire 30. In the steady state, an overcurrent is not generated.Because the heat generated at the interrupt wire 30 can be diffused viathe connection wires 40 and 50 during the steady state, a temperaturerise in the interrupt wire 30 can be restricted and a long-termreliability of the traction control device 20 can be increased.

Because the heat transmission restriction member 27 having the wirethickness thinner than wire thicknesses of the connection wires 40 and50 is disposed on the inside of the interrupt wire 30, thecross-sectional areas S1 a and S2 a of the interrupt wire 30 are easilydecreased compared with a case where the heat transmission restrictionmember 27 is not disposed. Specifically, transmission of the heatgenerated by the interrupt wire 30 can be restricted by the heattransmission restriction member 27. Thus, the variation in thetemperature rise of the interrupt wire 30 can be restricted.Additionally, because the wire thickness of the interrupt wire 30becomes smaller, the melt conductor generated by the melting of theinterrupt wire 30 has a smaller volume and adverse effect caused by aflow of the melt conductor to other electronic components 22 can berestricted.

Additionally, because the connection wires 40 and 50 have the greaterconductor volumes than the interrupt wire 30, the connection wires 40and 50 can store heat from the interrupt wire 30.

The power supply wire 23 is coupled with the battery 13, which suppliespower not only to the traction control device 20 but also to otherelectronic control devices 12, by the power supply path, and the fuse 14a for protecting the traction control device 20 and other electroniccontrol devices 12 is disposed on the power supply path. Even when ashort-circuit fault occurs in the traction control device 20 includingthe interrupt wire 30, the interrupt wire 30 melts. Thus, influence ofthe short-circuit fault on the power supply to other electronic controldevices 12 can be restricted.

A traction control device 20 according to a first modification of thefirst embodiment will be described with reference to FIG. 5A and FIG.5B. As shown in FIG. 5A, in the traction control device 20, connectionwires 40 and 50 may be partially arc-shaped. Specifically, theconnection wire 40 is partially arc-shaped (R-shape) so that an area ofa cross section, which is perpendicular to a direction from theinterrupt wire 30 to the power supply wire 23, gradually increasestoward the power supply wire 23. Similarly, the connection wire 50 ispartially arc-shaped (R-shape) so that an area of a cross section, whichis perpendicular to a direction from the interrupt wire 30 to the land26, gradually increases toward the land 26.

The connection wires 40 and 50 having above-described shape can restricta temperature decrease in the interrupt wire 30. Additionally, because aheat transmission path, which is extended in an arc manner, is securedby the connection wires 40 and 50, a local temperature rise in theinterrupt wire 30 can be restricted.

As shown in FIG. 5A, side ends of the connection wire 40 are smoothlyconnected with respective side ends of the interrupt wire 30 and thewire width of the connection wire 40 gradually increases toward thepower supply wire 23. Similarly, side ends of the connection wire 50 aresmoothly connected with respective side ends of the interrupt wire 30and the wire width of the connection wire 50 gradually increases towardthe land 26. Thus, when the interrupt wire 30 and the connection wires40 and 50 are formed using etching liquid, the etching liquid canuniformly flow at connecting portions of the interrupt wire 30 and theconnection wires 40 and 50. Accordingly, the etching liquid is lesslikely to stay at the connecting portions and a variation in the wirewidth of the interrupt wire 30 can be restricted. Thus, a decrease inthe interrupt performance by the interrupt wire 30 can be restricted.

As shown in FIG. 5B, in the traction control device 20 according to thefirst modification of the first embodiment, the connection wires 40 and50 may also be partially taper-shaped. Specifically, the connection wire40 is partially taper-shaped so that the area of the cross sectiongradually increases toward the power supply wire 23. Similarly, theconnection wire 50 is partially taper-shaped so that the area of thecross section gradually increases toward the land 26. The connectionwires 40 and 50 having a tapered-shape provide similar effects with theconnection wires 40 and 60 having an arc-shape.

A traction control device 20 according to a second modification of thefirst embodiment will be described with reference to FIG. 6. In thetraction control device 20, a plurality of interrupt wires 30 may bedisposed respectively to a plurality of electronic components 22. Ineach of the interrupt wires 30, at least a connection wire 40 or 50 isdisposed between an end of the interrupt wire 30 and the power supplywire 23 or a component-mounted wire, such as the land 26. As shown inFIG. 6, an interrupt wire 30 is electrically coupled with a land 26 a ofan electronic component 24 d via a connection wire 40 and is coupledwith the power supply wire 23 via a connection wire 50. Anotherinterrupt wire 30 is electrically coupled with the power supply wire 23via a connection wire 40.

A traction control device 20 according to a third modification of thefirst embodiment will be described with reference to FIG. 7. In thetraction control device 20, at least one interrupt wire 30 may becoupled between an array-type ceramic capacitor 24 f having a pluralityof outside electrodes and the power supply wire 23. The ceramiccapacitor 24 f is formed by arraying four multilayer capacitors in apackage. As shown in FIG. 7, the ceramic capacitor 24 f has four outsideelectrodes which are respectively mounted on lands 26 c to 26 f. Fourinterrupt wires 30 are disposed between respective lands 26 c to 26 fand the power supply wire 23. Each of the interrupt wires 30 is coupledwith the power supply wire 23 via the connection wire 40, and is coupledwith a corresponding land of the lands 26 c to 26 f via the connectionwire 50.

As described above, in a case where a plurality of interrupt wires 30 isdisposed on the circuit substrate 21, the variation in the temperaturerise in each of the interrupt wires 30 can be restricted by disposingthe connection wires 40 and 50 in each interrupt wire 30. Thus, thedecrease in the interrupt performance by the interrupt wires 30 can berestricted.

A traction control device 20 according to a fourth modification firstembodiment will be described. In the traction control device 20, theinterrupt wire 30 may be made of material, such as aluminum, having alower thermal conductivity than the connection wires 40 and 50.Accordingly, heat generated at the interrupt wire 30 by an overcurrentis less likely to be transmitted to the connection wires 40 and 50, andthereby the variation in the temperature rise of the interrupt wire 30can be restricted. Further, the decrease in the interrupt performance bythe interrupt wire 30 can be restricted.

Second Embodiment

A traction control device 20 a according to a second embodiment of thepresent disclosure will be described with reference to FIG. 8 and FIG.9.

The traction control device 20 a according to the present embodimentincludes connection wires 40 a and 50 a instead of the connection wires40 and 50 described in the forgoing embodiment.

As shown in FIG. 8 and FIG. 9, the connection wire 40 a includes a heatstorage portion 41 adjacent to the interrupt wire and a narrow-downportion 42 adjacent to the power supply wire 23. The narrow-down portion42 is designed so that a total cross-sectional area S3 a of a connectingportion of the connection wire 40 a with the power supply wire 23 issmaller than a cross-sectional area of a middle portion of theconnection wire 40 a, that is, a cross-sectional area S3 b of the heatstorage portion 41.

Similarly, the connection wire 50 a includes a heat storage portion 51adjacent to the interrupt wire 30 and a narrow-down portion 52 adjacentto the land 26. The narrow-down portion 52 is designed so that a totalcross-sectional area S4 a of a connecting portion of the connection wire50 a with the land 26 is smaller than a cross-sectional area of a middleportion of the connection wire 50 a, that is, a cross-sectional area S4b of the heat storage portion 51.

Thus, heat transmitted to the connection wire 40 a from the interruptwire 30 is less likely to be transmitted to the power supply wire 23 viathe narrow-down portion 42, and the heat storage portion 41 stores heat.Because the heat storage portion 41 stores heat from the interrupt wire30, when the interrupt wire 30 melts, a temperature of the heat storageportion 41 is relatively high. Thus, the variation in the temperaturerise of the interrupt wire 30 can be restricted, and a decrease in theinterrupt performance by the interrupt wire 30 can be restricted withcertainty. Additionally, by disposing the connection wire 50 a in asimilar manner with the connection wire 40 a, the variation in thetemperature rise of the interrupt wire 30 can be restricted, and adecrease in the interrupt performance by the interrupt wire 30 can berestricted with certainty.

By setting the interrupt wire 30 and the connection wires 40 a and 50 ato have a predetermined depth and to be made of a predeterminedmaterial, an interrupt condition is fixed so as to restrict thevariation, and a set of the interrupt wire 30 and the connection wires40 a and 50 a can be widely used. In addition, because heat storageamounts of the connection wires 40 a and 50 a can be respectivelycontrolled with volumes of the heat storage portions 41 and 51, themelting time of the interrupt wire 30 can be easily controlled.

Because the connecting portion of the connection wire 40 a with thepower supply wire 23 is formed as the two narrow-down portions 42, whenthe heat from the interrupt wire 30 is transmitted to the power supplywire 23 via the two narrow-down portions 42, the heat is transmitted tothe power supply wire 23 while being diffused in the narrow-downportions 42. Thus, a local temperature rise in the power supply wire 23can be restricted. Additionally, by disposing the connection wire 50 ain a similar manner with the connection wire 40 a, a local temperaturerise in the land 26 can be restricted.

The number of the narrow-down portions 42 of the connection wire 40 amay also be one or more than two depending on the interrupt condition.Similarly, the number of the narrow-down portions 52 of the connectionwire 50 a may also be one or more than two depending on the interruptcondition.

A traction control device 20 a according to a modification of the secondembodiment will be described with reference to FIG. 10A and FIG. 10B. Asshown in FIG. 10A, the heat storage portion 41 of the connection wire 40a and the heat storage portion 51 of the connection wire 50 a may bepartially arc-shaped. Specifically, the heat storage portion 41 of theconnection wire 40 a is partially arc-shaped (R-shape) so that an areaof a cross section, which is perpendicular to the direction from theinterrupt wire 30 to the power supply wire 23, gradually increasestoward the power supply wire 23. Similarly, the heat storage portion 51of the connection wire 50 a is partially arc-shaped (R-shape) so that anarea of a cross section, which is perpendicular to the direction fromthe interrupt wire 30 to the land 26, gradually increases toward theland 26.

As shown in FIG. 10B, the heat storage portion 41 of the connection wire40 a and the heat storage portion 51 of the connection wire 50 a mayalso be partially taper-shaped. Specifically, the heat storage portion41 of the connection wire 40 a is partially taper-shaped so that thearea of the cross section gradually increases toward the power supplywire 23. Similarly, the heat storage portion 51 of the connection wire50 a is partially taper-shaped so that the area of the cross sectiongradually increases toward the land 26.

Connection wires 40 a and 50 a having above-described shape can restricta temperature decrease in the interrupt wire 30. Additionally, because aheat transmission path, which is extended in an arc manner, is securedby the connection wires 40 and 50, a local temperature rise in theinterrupt wire 30 can be restricted. In particular, because the heattransmitted from the interrupt wire 30 can be transmitted uniformly inthe heat storage portions 41 and 51, the heat can be uniformly stored inthe heat storage portions 41 and 51.

The above-described configurations of the connection wires 40 a and 50 amay be applied to other embodiments and modifications.

Third Embodiment

A traction control device 20 b according to a third embodiment of thepresent disclosure will be described with reference to FIG. 11.

The traction control device 20 b according to the present embodimentincludes an interrupt wire 30 a instead of the interrupt wire 30described in the forgoing embodiments. In order to achieve a denselymounting, the power supply wire 23 is disposed between the lands 26 onwhich the outside electrodes 24 a of the ceramic capacitor 24 aremounted.

As shown in FIG. 11, the interrupt wire 30 a includes a first wiresection 31 and a second wire section 32 that is shorter than the firstwire section 31. The first wire section 31 and the second wire section32 are coupled to each other at a predetermined angle. The predeterminedangle is determined so that the first wire section 31 is coupled withthe power supply wire 23 and the second wire section 32 is coupled withthe land 26. For example, the predetermined angle is 90 degrees.

By bending the interrupt wire 30 a at the predetermined angle, a wirelength of the interrupt wire 30 a can be increased compared with a casewhere the interrupt wire 30 a has a straight shape while coupling thepower supply wire 23 and the land 26. Accordingly, a required wirelength of the interrupt wire 30 a can be secured in a limited mountingarea. Thus, the decrease in the interrupt performance by the interruptwire 30 a can be restricted and a size of the traction control device 20b can be decreased.

In the traction control device 20 b according to the present embodiment,the first wire section 31 is coupled with the power supply wire 23, andthe second wire section 32 is coupled with the land 26. Alternatively,the first wire section 31 may be coupled with the land 26, and thesecond wire section 32 may be coupled with the power supply wire 23.Further, a position of the predetermined angle at which the first wiresection 31 and the second wire section 32 are coupled to each other maybe set according to positions of the power supply wire 23 and the land26. In FIG. 11, the interrupt wire 30 a is coupled with the power supplywire 23 via the connection wire 40. The interrupt wire 30 a may becoupled with the land 26 via the connection wire 50. The first wiresection 31 may have a arrow portion at a middle portion of an entirelength of the interrupt wire 30 a including the first wire section 31and the second wire section 32. The narrow portion has a wire widthnarrower than the other portion of the first wire section 31.Accordingly, when the interrupt wire 30 a melts, the interrupt wire 30 ais likely to melt at the narrow portion. Thus, a variation in a meltedportion can be restricted. In order to restrict a heat concentration ata connecting portion of the first wire section 31 and the second wiresection 32, the connecting portion may be formed in such a manner thatthe connecting portion has similar wire widths with the first wiresection 31 and the second wire section 32 at adjacent two side ends. Theabove-described configuration of the interrupt wire 30 a may be appliedto other embodiments and modifications.

Fourth Embodiment

A traction control device 20 c according to a fourth embodiment of thepresent disclosure will be described with reference to FIG. 12 and FIG.13.

In the traction control device 20 c according to the present embodiment,a solder resist layer 28, which functions as a protective layer toprotect the surface of the circuit substrate 21, defines an openingportion 28 a so that at least a portion of the interrupt wire 30 isexposed outside. In FIG. 12, the solder resist layer 28 is not shown forconvenience of drawing.

As shown in FIG. 12 and FIG. 13, the solder resist layer 28 defines theopening portion 28 a so that the middle portion of the entire length ofthe interrupt wire 30, which is most likely to generate heat, is exposedoutside. Reasons of providing the opening portion 28 a will be describedwith reference to FIG. 14 and FIG. 15.

In a device shown in FIG. 14, a part of a test interrupt wire 101 isexposed outside through a test opening portion 102 defined by a solderresist layer. The test interrupt wire 101 is supplied with apredetermined current, and an interrupting current I with which the testinterrupt wire 101 melts and a melting time t when the test interruptwire 101 melts are measured. Furthermore, an interrupting current I anda melting time t of a test interrupt wire 101 in a case where a solderresist layer does not define a test opening portion 102 are alsomeasured. The test interrupt wire 101 has an entire length L1 of 2.55 mmand has a width W1 of 0.25 mm. The test opening portion 102 has anopening length L2 of 0.6 mm in a direction parallel to a lengthdirection of the test interrupt wire 101 and has an opening width W2 of0.25 mm in a width direction of the test interrupt wire 101. In FIG. 14,the opening width W2 is drawn as being longer than the with W1 forconvenience of drawing.

In FIG. 14, a bold solid line S1 shows a relationship between theinterrupting current I and the melting time t of the test interrupt wire101, a part of which is exposed through the test opening portion 102,and a range between bold dashed lines centered on the bold solid line S1shows a variation range of the melting time t with respect to theinterrupting current I. A thin solid line 82 shows a relationshipbetween the interrupting current I and the melting time t of the testinterrupt wire 101 in a case where a test opening portion 102 is notdefined, and a range between thin dashed lines centered on the thinsolid line 82 shows a variation range of the melting time t with respectto the interrupting current I.

As shown in FIG. 14, at the same interrupting current, the melting timet decreases and the variation range decreases when the test openingportion 102 is defined by the solder resist layer. In contrast, in thecase where the test opening portion 102 is not defined by the solderresist layer, the melting time t of the test interrupt wire 101increases in each overcurrent range and the variation range increasescompared with the case where the test opening portion 102 is defined.This is because a melt conductor generated by melting of the testinterrupt wire 101 flows from the test opening portion 102 and the meltconductor is less likely to stay at a position of the test interruptwire 101 before melting.

Thus, when at least a part of the interrupt wire 30 is exposed throughthe opening portion 28 a, the melting time t decreases, the overcurrentprotection action can be achieved early, and a temperature rise in aprotected component can be restricted. Furthermore, a time for which avoltage of the power supply wire 23 decreases due to interruption by theinterrupt wire 30 can be reduced. In addition, because the variation ofthe melting time t decreases, a capacity of a stabilizing capacitor thatis designed in view of the melting time of the interrupt wire 30 in eachdevice or each circuit can be reduced, and a cost and a size can bereduced, Furthermore, because the melting time t decreases also in arated region of current, a circuit can be designed more freely.

Thus, when the interrupt wire 30 melts in accordance with heat generatedby the overcurrent, a melt conductor generated by melting of theinterrupt wire 30 flows from the opening portion 28 a. Accordingly, themelt conductor is less likely to stay at a position of the interruptwire 30 before melting, variations in the melt position and the meltingtime due to stay of the melt conductor can be restricted, and a decreasein an interrupt performance by the interrupt wire 30 can be restricted.

In the traction control device 20 c according to the present embodiment,the opening portion 26 a is defined so that the middle portion of theinterrupt wire 30 which is most likely to melt is exposed outside.Alternatively, the opening portion 28 a may be defined so that anotherportion of the interrupt wire 30 or the whole interrupt wire 30 isexposed outside. The above-described configuration of the openingportion 28 a, through which at least a portion of the interrupt wire 30is exposed, may be applied to other embodiments and modifications.

A traction control device 20 c according to a modification of the fourthembodiment will be described with reference to FIG. 16. As shown in FIG.16, a pair of adherent wires 60 may be disposed adjacent to theinterrupt wire 30. The adherent wire 60 can work as an adherent memberor an adsorption member to which the melt conductor generated by meltingof the interrupt wire 30 adheres. The adherent wire 60 may be made ofthe same material as the power supply wire 23. When the melt conductorof the high temperature is generated by melting of the interrupt wire30, the melt conductor flow on the surface of the circuit substrate 21and adheres to the adherent wires 60 adjacent to the interrupt wire 30.

Accordingly, the melt conductor is held by the adherent wires 60 andloses flowability by releasing heat and being hardened. Thus, a decreasein the interrupt performance by the interrupt wire 30 can be restricted,and influence of the flow of the melt conductor on other electroniccomponents can be restricted. The adherent wires 60 may be disposed withrespect to the interrupt wire 30, a part of which is exposed outsidethrough the opening portion 28 a, the adherent wires 60 may also bedisposed with respect to the interrupt wire 30 whose surface is entirelycovered with the solder resist layer 28, and the adherent wires 60 mayalso be disposed with respect to the interrupt wire 30 not covered withthe solder resist layer 28.

Fifth Embodiment

An electronic control device 110 according to a fifth embodiment of thepresent disclosure will be described with reference to FIG, 17. Theelectronic control device 110 includes a substrate 120 and circuitblocks 130, 140, 150 disposed on the substrate 120. The circuit block130 performs a similar function to the traction control device 20according to the first embodiment. The circuit blocks 140, 150 performdifferent functions from the circuit block 130. The different functionsare more important than the function of the circuit block 130. Forexample, the circuit block 140 performs a function corresponding to theengine ECU, and the circuit block 150 performs a function correspondingto the brake ECU.

The circuit blocks 130, 140, 150 are electrically coupled with the powersupply wire 23, which supplies electric power from the battery 13, viabranch wires 131 141, 151, respectively. The above-described interruptwire 30 is disposed on the branch wire 131 coupled with the circuitblock 130 so as to function as overcurrent protection for the circuitblock 130. On the power supply wire 23, an interrupt wire 122 thatfunctions as overcurrent protection for the substrate 120 is disposed.In other words, the interrupt wire 122, which protects the substrate 120including all the circuit blocks 130-150, and the interrupt wire 30,which protects the circuit block 130, are disposed on the substrate 120.

Accordingly, even, when overcurrent is caused by a short-circuit faultin the circuit block 130 and the interrupt wire 30 melts due to theovercurrent, the circuit blocks 140, 150 are still electrically coupledwith the power supply wire 23 via the branch wires 141, 151. Thus, onlythe circuit block 130 coupled with the melt interrupt wire 30 stops andthe circuit blocks 140, 150 keep operating. In particular, since thefunction of the circuit block 130 is less important than the functionsof the circuit blocks 140, 150, influence of the stop of the lessimportant circuit block 130 on the functions of the more importantcircuit blocks 140, 150 can be restricted. When an overcurrent is causedby a short-circuit fault in the circuit blocks 140, 150 without theinterrupt wire 30, the overcurrent flows to the power supply wire 23,the interrupt wire 122 melts, and the circuit blocks 130, 140, 150 aredeactivated. Thus, the overcurrent is less likely to flow to othercircuit block.

Especially in a case where a wire width of the interrupt wire 30 issmaller than a wire width of the interrupt wire 122 so that a currentvalue at interruption by the interrupt wire 30 is smaller than a currentvalue at interruption by the interrupt wire 122, when an overcurrent iscaused by a short-circuit fault in the circuit block 130, the interruptwire 30 melts earlier than the interrupt wire 122 with certainty. Thus,the influence on other circuit blocks 140, 150 can be restricted withcertainty. The above-described configuration including two interruptwires on one substrate may be applied to other embodiments andmodifications.

Other Embodiments

The present invention is not limited to the above-describe embodimentsand the above-described modifications may include various changes andmodifications. For example, the connection wire 40 coupled at one end ofthe interrupt wire 30 may be electrically coupled with the common wire,which is shared by the electronic components 22 to be protected againstovercurrent, instead of the power supply wire 23.

The connection wire 50 coupled at the other end of the interrupt wire 30may be electrically coupled with a component-mounted wire on which anelectronic component is disposed, such as an internal layer fullycovered with a protective layer made of, for example, solder resist.

At least one of the connection wires 40 and 50, and the interrupt wire30 may be provided for each substrate for overcurrent protection of theelectronic control devices 12 including the engine ECU the brake ECU,the steering ECU, the body ECU, and the navigation ECU.

The above-described other embodiments may also be applied to theconnection wires other than the connection wires 40 and 50, and theinterrupt wires other than the interrupt wire 30.

1-14. (canceled)
 15. An electronic control device comprising: asubstrate; a plurality of component-mounted wires disposed on thesubstrate; a plurality of electronic components mounted on therespective component-mounted wires; a common wire disposed on thesubstrate and coupled with each of the electronic components; aninterrupt wire coupled between one of the component-mounted wires andthe common wire, the interrupt wire configured to melt in accordancewith heat generated by an overcurrent so as to interrupt a couplingbetween the one of the component-mounted wires and the common wire viathe interrupt wire; a connection wire via which the interrupt wire iscoupled with a connection object that is one of the common wire and theone of the component-mounted wires; a solder disposed between each ofthe electronic components and a corresponding one of thecomponent-mounted wires, the solder having a lower melting point thanthe interrupt wire; and a protective layer covering a surface of thesubstrate including the interrupt wire, the protective layer defining anopening portion, and only a portion of the interrupt wire in a lengthdirection of the interrupt wire being exposed through the openingportion, wherein the connection wire has a first end portion adjacent tothe interrupt wire and a second end portion adjacent to the connectionobject, wherein a cross-sectional area of the first end portion issmaller than a cross-sectional area of the second end portion, andwherein the interrupt wire is disposed adjacent to the electroniccomponent other than the electronic component that is coupled with theinterrupt wire, and the interrupt wire is disposed adjacent to a wireother than the component-mounted wire and the common wire that arecoupled with the interrupt wire.
 16. The electronic control deviceaccording to claim 15, further comprising an interrupt wire and aconnection wire coupled between another of the component-mounted wiresand the common wire.
 17. The electronic control device according toclaim 15, wherein the interrupt wire includes a first wire section and asecond wire section that is shorter than the first wire section, andwherein the first wire section and the second wire section coupled witheach other at a predetermined angle, the predetermined angle isdetermined so that one of the first wire section and the second wiresection is coupled with the common wire and the other is coupled withthe one of the component-mounted wires.
 18. The electronic controldevice according to claim 15, further comprising an adherent memberdisposed adjacent to the interrupt wire, the adherent member configuredso that a melt conductor generated by melting of the interrupt wireadheres to the adherent member.
 19. The electronic control deviceaccording to claim 15, wherein the common wire is a power supply wire.20. A control system comprising: a power supply path coupled with apower source; a fuse disposed on the power supply path; a device coupledwith the power source by the power supply path via the fuse; and theelectronic control device according to claim 19, wherein the powersupply wire in the electronic control device is coupled with the powersource by the power supply path via the fuse.
 21. The electronic controldevice according to claim 15, further comprising a heat transmissionrestriction member disposed on an inside of the interrupt wire so as torestrict transmission of heat toward an inside of the substrate, whereinthe interrupt wire has a smaller thickness than the connection wire in adirection perpendicular to the substrate, wherein the interrupt wire hasan outside surface that is partially exposed to outside via the openingportion and an inside surface disposed opposite to the outside surface,and wherein the inside surface is contacted with the heat transmissionrestriction member so that the interrupt wire is attached to thesubstrate.
 22. The electronic control device according to claim 15,wherein the opening portion has a width greater than a width of theinterrupt wire.